This invention relates to devices for providing information, in the form of electrical signals, about the position of a selected touch point serving as a source or sink of electric current relative to a current-carrying resistance or impedance element. In particular, it relates to devices for converting selected touch points or positions on a surface (reflecting hand motions) into electrical signals to provide an interface between man and machine.
As used herein, the term "a selected touch point" means a point on a surface selectively touched by a portion of a human body, particularly a finger or toe, or a point on a surface touched by an instrument held in the hand or other portion of a human body and controlled by the human, or a point on a surface contacted by a mechanical contrivance which is guided by a human. In the context of this invention "selected" means the direction by the human intellect of the point on the surface that is touched.
In the context of this invention the term "point" encompasses the area of contact between a human finger and a surface, or the area of contact of an implement, such as the pointed end of a stylus, with a surface. Thus, it is intended that the term "selected touch point" exclude non-physically contacting transfers of electrical energy between the touch panel surface and a sensing device or transducer. As used herein the term "current collecting" includes electrical current passing to or from the impedance surface.
This invention is an improvement over the touch panels described in my U.S. Pat. Nos. 4,071,691 and 4,129,747, and my pending patent application Ser. No. 867,256, now U.S. Pat. No. 4,198,539, all incorporated herein by reference. As discussed in my aforementioned patent application Ser. No. 867,256, the phase of the field produced in the resistive surface was not a linear function of position on the surface, introducing an error in the output function unless special techniques were used to compensate for the error.
The present invention substantially overcomes the limitations of that earlier system. It does not require a pickup surface and is therefore easier to package and manufacture than the earlier system. It also has improved linearity. It will therefore be seen that it is an improvement in the art of human-machine interfacing.
An article "A Position-Sensitive Detector for Electrons," by C. D. Moak, S. Datz, F. Garcia Santibanez, and T. A. Carlson, in the Journal of Electron Spectroscopy and Related Phenomena, No. 6, 1975, pp. 151-156, discloses the principle of locating, on one axis, the point on a linear resistive anode at which electrons emerge from a chevron multiplier (which was impinged upon by an electron beam) in a high-resolution electron spectrometer. In such system, a high D. C. voltage is required between the electron multiplier and the resistive strip collector.